This proposal is concerned with the effects of phospholipase A (PL-A) on periodontal tissues. A survey of supra- and subgingival microorganisms for their ability to synthesize PL-A will be continued. Purification of PL-A from Bacteroides melaninogenicus will also be concluded. The purified enzymes will be used to test their ability to hydrolyze epithelial cell membrane phospholipids. The free fatty acids resulting from this action will be analyzed to determine whether prostaglandin precursor may be released into the environment by these enzymes.